Prosthetic joints are biomedical devices that replace all or a portion of bone and cartilage in a joint, and thereby restore, improve, or prolong the useful function of that joint. Prosthetic joints are commonly implanted into human patients to mitigate degraded function of such major joints as hips, knees, shoulders, and the like. Like biological joints, prosthetic joints bear mechanical loads while facilitating relative movement of the opposed portions of the joint. This capability of a prosthetic joint enables critical locomotor activities, where for example a knee prosthetic joint can facilitate walking, bending the knees to stoop, and any other common function of the knee joint.
The use of prosthetic joints continues to grow, in part due to increasing numbers of elderly and in part because the benefits of joint prostheses are being extended to younger patients. Wear life of a prosthetic joint can be important in elderly patients, as revision procedures to replace worn joints become less-well tolerated with increasing age. Wear life is similarly important in younger prosthetic recipients, as the joints are exposed to greater mechanical stresses associated with more athletic lifestyles of the young and there may be a need for the prosthetic joint to last longer as the recipient ages.
Unlike biological joints, prosthetic joints do not have means of self-repair and are therefore subject to wear. Wear includes attrition of prosthetic joint materials due to mechanical and/or chemical effects on the joint surfaces that rub against each other. As wear proceeds, the function of a prosthetic joint may degrade to a significant degree and may require replacement in a revision operation. The worn prosthetic joint may also become more susceptible to catastrophic failure, and particulate materials worn from the prosthetic joint components may damage nearby tissues, potentially causing osteonecrosis and consequent joint failure.
Prosthetic joint wear is a complex process, and may be driven by mechanical stresses developed on the joint. These stresses include static stresses (e.g., such as would be developed by standing) and dynamic stresses (e.g., as would be caused by walking or running). These stresses wear prosthetic joint components and limit the joint's useful service life.
Therefore, it would be advantageous to have a prosthetic joint that has enhanced wear resistance for extended usefulness without needing a replacement.